patch: check for c99 support

[ky0ko]

as of version 4.3, with the inclusion of gnulib, make now appears to require 
c99 support in order to be compiled correctly.

since this is the case, the configure script should check if flags are 
necessary to enable c99 support, as several non-gnu compilers do not enable it 
by default.

--- make-4.3/configure.ac       2020-01-19 12:32:59.000000000 -0800
+++ make-4.3.new/configure.ac   2020-05-28 18:02:55.214822187 -0700
@@ -37,6 +37,8 @@ AM_INIT_AUTOMAKE([1.16.1 foreign -Werror
 # Checks for programs.
 AC_USE_SYSTEM_EXTENSIONS
 AC_PROG_CC
+# C99 is needed as of version 4.3
+AC_PROG_CC_C99
 
 # Configure gnulib
 gl_EARLY